BERLIN (AP) — Flights to and from Frankfurt Airport have been interrupted briefly after two drones were seen in the area.

The news agency dpa reported that operator Fraport said takeoffs and landings at Germany's busiest airport were suspended as a precaution for 29 minutes late Friday afternoon. They resumed after federal police found no more sign of the drones.

The popularity of drones makes them a growing threat to aviation.

More than 100,000 travelers were stranded or delayed for days right before Christmas after drone sightings near London's Gatwick, Britain's second-busiest airport. No one has been arrested over the incident, which saw the airport shut for parts of three days.